[clang] [HLSL] Rewrite semantics parsing (PR #152537)

[Chris B via cfe-commits]

================
@@ -1513,29 +1517,71 @@ bool SemaHLSL::diagnosePositionType(QualType T, const ParsedAttr &AL) {
   return true;
 }
 
-void SemaHLSL::handleSV_PositionAttr(Decl *D, const ParsedAttr &AL) {
-  auto *VD = cast<ValueDecl>(D);
-  if (!diagnosePositionType(VD->getType(), AL))
-    return;
-
-  D->addAttr(::new (getASTContext()) HLSLSV_PositionAttr(getASTContext(), AL));
-}
+void SemaHLSL::diagnoseSystemSemanticAttr(Decl *D, const ParsedAttr &AL,
+                                          std::optional<unsigned> Index) {
+  StringRef SemanticName = AL.getAttrName()->getName();
 
-void SemaHLSL::handleSV_GroupThreadIDAttr(Decl *D, const ParsedAttr &AL) {
   auto *VD = cast<ValueDecl>(D);
-  if (!diagnoseInputIDType(VD->getType(), AL))
-    return;
-
-  D->addAttr(::new (getASTContext())
-                 HLSLSV_GroupThreadIDAttr(getASTContext(), AL));
-}
+  QualType ValueType = VD->getType();
+  if (auto *FD = dyn_cast<FunctionDecl>(D))
+    ValueType = FD->getReturnType();
+
+  bool IsOutput = false;
+  if (HLSLParamModifierAttr *MA = D->getAttr<HLSLParamModifierAttr>()) {
+    if (MA->isOut()) {
+      IsOutput = true;
+      ValueType = cast<ReferenceType>(ValueType)->getPointeeType();
+    }
+  }
 
-void SemaHLSL::handleSV_GroupIDAttr(Decl *D, const ParsedAttr &AL) {
-  auto *VD = cast<ValueDecl>(D);
-  if (!diagnoseInputIDType(VD->getType(), AL))
+#define CHECK_OUTPUT_FORBIDDEN(AL)                                             \
+  if (IsOutput) {                                                              \
+    Diag(AL.getLoc(), diag::err_hlsl_semantic_output_not_supported) << AL;     \
+  }
+
+  Attr *Attribute = nullptr;
+  if (SemanticName == "SV_DISPATCHTHREADID") {
+    diagnoseInputIDType(ValueType, AL);
+    CHECK_OUTPUT_FORBIDDEN(AL);
+    Attribute = createSemanticAttr<HLSLSV_DispatchThreadIDAttr>(AL, Index);
+  } else if (SemanticName == "SV_GROUPINDEX") {
+    CHECK_OUTPUT_FORBIDDEN(AL);
+    Attribute = createSemanticAttr<HLSLSV_GroupIndexAttr>(AL, Index);
+  } else if (SemanticName == "SV_GROUPTHREADID") {
+    diagnoseInputIDType(ValueType, AL);
+    CHECK_OUTPUT_FORBIDDEN(AL);
+    Attribute = createSemanticAttr<HLSLSV_GroupThreadIDAttr>(AL, Index);
+  } else if (SemanticName == "SV_GROUPID") {
+    diagnoseInputIDType(ValueType, AL);
+    CHECK_OUTPUT_FORBIDDEN(AL);
+    Attribute = createSemanticAttr<HLSLSV_GroupIDAttr>(AL, Index);
+  } else if (SemanticName == "SV_POSITION") {
----------------
llvm-beanz wrote:

I worry a little bit about this if/else statement just becoming a bit of a mess, but it's probably fine for now. We can always refactor it later as it grows and we have a clearer understanding of all the cases it needs to handle.

https://github.com/llvm/llvm-project/pull/152537